COVID-19 and the Spanish Flu Pandemic of 1918-19

October 1918 was the height of the Spanish influenza pandemic in Cape Town, South Africa. A leading community worker asked his good friend Dr. Frederick Willmot, the state’s assistant medical officer of health, the following: “Will you answer a straightforward question? Are we going to be wiped out?” Willmot hesitated before replying, “I’ll tell you what I would not tell any other man in the Union of South Africa, for the first time in my life I’m panicky, and believe we are.”

What does the dire Spanish flu calamity teach us about how to combat COVID-19 more effectively?

In short, it warns us that when a highly infectious epidemic breaks out, a country cannot act fast enough before the disease enters the runaway stage. Missing this window of opportunity makes curbing it thereafter extremely difficult — if not impossible.

Similarities Between the Spanish Flu and COVID-19

Back in 1918, in the midst of World War I, the world was slow in its response to the disease, which had broken out in the military camps of the United States and then spread to Europe. In neutral Spain, the uncensored press had given it prominence, resulting in the misnomer “Spanish” flu. From Europe, it rapidly swept around the globe in less than a year, killing more than 50 million people — roughly 3 percent of the earth’s population. It was the worst pandemic of modern times in terms of its speed, range, and toll, which dwarfed the number of battlefield deaths in World War I.

On the face of it, the two pandemics have much in common. Both, it would seem, originated in what is termed a “zoonotic spillover,” which refers to the transmission or crossover of a virus from an animal reservoir to humans (influenza from aquatic birds and SARS-Cov2 probably originally from bats). Both were and are highly infectious, being spread through the air by coughing or sneezing (i.e., aerosol or droplet infection), or by touching infected surfaces. By these means, the Spanish flu and COVID-19 raced around the globe at the speed of the fastest transport system of the day (steamships and steam locomotives in 1918, and jet aircraft in 2020). Both produced symptoms like difficulty in breathing, fever, coughing and sneezing, while both could open a pathway to pneumonia and death.

Just like the Spanish flu, there is currently no preventive vaccine for COVID-19, and in both cases treatment was primarily supportive and aimed at alleviating symptoms. Both pandemics swamped existing health facilities. In both cases — as in all epidemics — people looked to assign blame for causing the pandemic, with those blamed (“them”) usually being individuals or countries deemed neglectful of public health or hostile to “us” for some nefarious reason.

Differences Between the Spanish Flu and COVID-19

However, probing below these features reveals significant differences between the two pandemics, which go well beyond the 102 years separating them and their respective contexts. These differences are important and useful in providing perspective on the current crisis.

Firstly, the incubation periods for the Spanish Flu and COVID-19 differ markedly. The incubation period of the virulent Spanish flu was very short — a day or two — while that of COVID-19 can stretch to a fortnight, facilitating its unnoticed, asymptomatic spread or “stealth transmission,” as it has been termed. That, plus the speed of international travel today, helps to account for the galloping pace at which COVID-19 has spread compared to the Spanish flu.

Secondly, the first two waves of the Spanish flu were not caused by an identical influenza virus. The causative pathogen of the first wave from March to June 1918 (which yielded the inaccurate tag “Spanish”) was certainly very infectious, but it was far less lethal than that which drove the second wave from August to December. The latter combined both infectiousness and lethality and, consequently, was responsible for most of the 50 million deaths attributed to the pandemic. As far as can be determined at this distance in time, its lethality arose from the fact that it penetrated deep into a victim’s lungs straightaway, where its virulence could either trigger an overreaction into overdrive by the immune system, filling the lungs with liquid antibodies that caused acute respiratory distress, or make the victim susceptible to bacterial pneumonia. Thus far, it seems that the COVID-19 coronavirus has not mutated into a killer of the same intensity, perhaps because it does not immediately penetrate the lungs, thereby giving the immune system a chance to counter it before it seriously affects the respiratory system.

This difference is evident in the age profile of those claimed by the two pandemics. In 1918, mortality was highest by far among young adults aged 18-40, whose immune systems were very robust and which consequently over-responded excessively, often with fatal results. So far in 2020, the elderly whose immune systems are on the wane and the immunocompromised of all ages have made up the bulk of the novel coronavirus dead.

The overall case fatality rates of the two pandemics — insofar as the official figures can be relied on — also show a sharp distinction. In the countries hit hardest by COVID-19 that have credible data — Italy and Spain — case fatalities appear to be between 11 and 8.5 percent, respectively, as of late March 2020. In the United Kingdom and France, case fatality rates are around 6 percent. In 1918, even though the statistics are much less reliable, it is clear that the worst case fatality rates were of a different order, with Tahiti at 20 percent and Western Samoa at 24.7 percent.

That such extensive case-fatality rates for COVID-19 are so easily available points to a very different public health context in which the two pandemics have played out. In 1918, the causative pathogen of Spanish flu, the influenza A virus (H1N1), had not yet been discovered — indeed, the existence of viruses was not yet known — and there was no overarching international health authority to collect, collate, and circulate data. World War I was still under way, putting strong military and political pressure not to make the extent and gravity of the pandemic known lest it alert the enemy to possible military weakness. Within many countries, public health systems outside of the military were very rudimentary and identification, isolation, contact tracing, and quarantining were impracticable given the severity of disruption caused by the Spanish flu. Ultimately, the needs of the military trumped any idea of restricting recruitment, training, and the dispatch of soldiers aboard overcrowded troop trains and troopships to the battlefield.

This stands in sharp contrast to the situation in the world of 2020, with a ubiquitous World Health Organization, with its International Health Regulations platform, and states that are willing to implement draconian measures in order to safeguard the health of their populations and economies. They may be involved in total war, as their predecessors were in 1918, but the world now faces a war against a virus, not humans.

Lessons for the Present Crisis

Clearly, though the two pandemics share some features, they also differ in very significant ways. Is there thus any benefit in comparing the two? My answer is “yes,” on two scores.

Firstly, because doing so emphasizes the critical importance — as in all infectious diseases — of strictly enforcing isolation, quarantine, and social distancing early enough to check the runaway spread of the disease. Secondly, and perhaps more fundamentally, because the catastrophe of the Spanish flu is a dire warning 102 years later as to what may happen if vigorous measures of prevention and containment are not enforced now. The world should take and implement hard decisions immediately to avoid an even greater catastrophe later — millions of lives are at risk.